Various technologies have been proposed with regard to legged robots, including, for example, that taught by Japanese Laid-Open Patent Application No. 3-184782.
In Japanese Laid-Open Patent Application No. 3-184782, in order to reduce the inertial mass of a leg (leg linkage), the drive source (motor) for driving the joint connecting the body and the leg installed on a pelvic plate that is one part of the body of the robot. In the interest of high reduction ratio and to increase space utilization efficiency in a legged robot, a speed reducer having a high reduction gear ratio and coaxial input and output, such as a Harmonic Drive (harmonic speed reducer; trade name), is ordinarily used to reduce the speed of the output (rotation) of the drive source and transmit it to the joint.
In the aforesaid technology, removal of a leg requires that the speed reducer at the pelvic plate be disassembled into its constituent elements (flexspline and circular spline in the case of a Harmonic Drive), and during reassembly the procedure has to be conducted in reverse, which is troublesome.
In particular, ease of maintenance is not necessarily satisfactory because the flexspline is inserted into the circular spline with their gears meshed, so that disassembly is relatively easy but assembly must be conducted by engaging the gears. In addition, the pelvic plate must also be removed from the body of the robot when adjusting the tension of the belt that transmits the drive force from the drive source to the speed reducer, which is troublesome.